1. Field of the Invention
This invention relates to slide fasteners and more particularly to a separable type slide fastener suitable for use in jackets and the like garment article to facilitate the removal thereof from the user. The invention is more specifically directed to a separable slide fastener of the type carrying coupling element rows in a meandering or zig-zag formation.
2. Prior Art
Various separable slide fasteners have been proposed, a typical example of which is provided with a separable bottom-end-stop assembly including a pin member attached to one of a pair of fastener stringers and a socket member to the other stringer, the pin being releasably engageable with the socket to join the respective lower ends of the stringers. Such known separable bottom-end-stop assemblies were successful when applied to slide fasteners carrying coupling elements of a helical coil structure, but were not very satisfactory when applied to slide fasteners having meander or zig-zag shaped continuous coupling elements mounted astride both sides of the fastener tapes. This is because more stresses would be required for the latter type of fastener to bend or flex along an axis vertical to the plane of the fastener with the results that the fastener stringers once coupled together are, when such stresses are exerted, apt to separate unintentionally starting with the first terminal or lowermost one of the coupling elements immediately adjacent the bottom-end-stop assembly. Such unintentional separation of the stringers is often referred to as "chain crack".
To cope with the above "chain crack" problem, there has been proposed a separable slide fastener, as disclosed in U.S. Pat. No. 3,377,668, in which a separable bottom-end-stop assembly has a pin member on one stringer and a socket with pin on the other stringer, the pin member including a projection arranged to come under and engage the lower portion of a coupling head of the lowermost coupling element contiguous with the socket pin. This arrangement is effective in combating lateral pull on the fastener but not quite for overcoming stresses tending to flex the fastener laterally across inasmuch as the projection merely rests underneath the coupling head of the coupling element. To further assure retention of the lowermost element with respect to the projection of the pin member, there is provided in the socket pin a groove configured to receive a corresponding rail-like portion of the pin member with a tight interlocking fit. This arrangement is not only costly but also would involve increased resistance to sliding coupling and uncoupling of the pin and socket members.